Late Diagnosis of Klinefelter Syndrome: Overcoming Phenotypic Variability and Diagnostic Oversights

We report a case of Klinefelter syndrome (KS) diagnosed in adulthood, emphasizing the impact of phenotypic variability and the declining reliance on physical examination in delayed recognition. A 27-year-old male with obesity, low libido, and biochemical and clinical primary hypogonadism was found to have 47, XXY karyotype, consistent with KS. His hypogonadism was initially attributed to obesity and overlooked, despite classic signs of a micropenis and small testes. The case highlights the importance of physical examination, comprehensive history, and clinician awareness in diagnosing KS, particularly in atypical presentations. KS is associated with increased risks of osteoporosis, cardiovascular disease, and psychosocial challenges. Raising awareness and focusing on physical examinations can improve diagnostic timing and reduce complications.